QPainter, scale(), and setFont()

[jacek]

Try this:

void paintEvent( QPaintEvent * )
{
   QPainter p( this );
 
   p.save();
 
   // set up "traditional" coordinate system
   p.setWindow( -10, -10, 20, 20 );
   p.scale( 1.0, -1.0 );
   QTransform t = p.combinedTransform();
 
   // draw the graph
   p.drawLine( 0, 0, 5, 5 );
 
   // revert to the default coordinate system
   p.restore();
 
   // draw labels in the Right Place(tm) using t transform
   QPoint pt( 7, 7 );
   p.drawText( t.map( pt ), "xxx" );
}

void paintEvent( QPaintEvent * )
{
   QPainter p( this );

   p.save();

   // set up "traditional" coordinate system
   p.setWindow( -10, -10, 20, 20 );
   p.scale( 1.0, -1.0 );
   QTransform t = p.combinedTransform();

   // draw the graph
   p.drawLine( 0, 0, 5, 5 );

   // revert to the default coordinate system
   p.restore();

   // draw labels in the Right Place(tm) using t transform
   QPoint pt( 7, 7 );
   p.drawText( t.map( pt ), "xxx" );
}

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Instead of using save()/restore() you can prepare the right QTransform yourself and map all points.

Another solution is to scale the font, but it might not work with all fonts. Also take a look at Qwt.